In an attempt to prolong duration of pharmacological effects and to reduce side effects of drugs, percutaneous administration of drugs has recently been increasingly used in place of oral administration or injection. Further, selection of drugs to be administered percutaneously, which had been confined to topical ones, such as antiinflammatory analgesics, has been widened to include an increasing number of systemic drugs. However, it has been extremely difficult to prevent reduction of the content of an active ingredient in preparations with the passage of time, praticularly in that it has been difficult to stably maintain the active ingredient for a long period to time.
Preparations for percutaneous administration containing clonidine or its hydrochloride, which is a percutaneously absorbable systemic drug, are disclosed in U.S. Pat. No. 4,201,211 (corresponding to Japanese Patent Publication No. 20129/79) and Japanese Patent Application (OPI) No. 150614/82 (the term "OPI" as used herein refers to a "published unexamined application"). These preparations achieve the prescribed objects to some extent in terms of controlled release or pharmacological effect, but are still unsatisfactory in terms of stability of the active ingredient for a prolonged period of time.